Protective grid for geiger-mueller tubes



Oct. 26, 1948. M T N 2,452,524

PROTECTIVE GRID FOR GEIGER-MUELLER TUBES Filed Jan. 2, 1948 INVENTOR.

Herbert L latte ATTORNEY Patented Oct. 26, 1948 PROTECTIVE GRID FOR GEIGER-MUELLER TUBES Herbert Metten, Boston, Mass., assignor to Sylvania Electric Products Inc., Salem, Mass., a corporation of Massachusetts Application January 2, 1948, Serial No. 93

l Claims. (Cl. 250--27.5)

. I a E This invention relates to ray counters, and particularly to Geiger-Mueller counters of the type having a thin metal window for admitting beta rays.

Such counters generally have an anode and cathode near the, metal window, which may cause arcing to the window with consequent damage thereto.

My inventioncomprises placing a wire or grid between the cathode and anode near the window and connected to the cathode to prevent arcing to the window.

Manyobjects-features and advantages of the invention willbe apparent from the following specification taken in connection with the accompanying drawing n which:

Figure 1 is asectional. side view 01' the invention; and

Figure 2 is a view showing the cathode, anode and grid wire in plan view, just inside the win- In the figures, the glass envelope I has the two lead-in wires '2 and 3 sealed therethrough at one end, the lead-in wire 2 being bent transversely inside the tube, i. The U-shaped wire 4, attached thereto supports the cylindrical metal cathode, the insulating glass beads 5 and 6 extending from the ends of-said wire, as shown, to the wires 1 and 8 welded't'o said cathode cylinder 9, which is further supported by the lead-in wire 3 welded thereto at a'diiferent point and in electrical contact with said cathode. The lead-in wire 3 being protected by a glass bead around it up to a point near the cathode.

The support 'wire l0 extending from the bent portion ii orlead-in wire 2 extends into the oathode cylinder' BItermInating near the middle thereof in a flnewfre of about 0.006 inch diameter which acts as anode and terminates in a glass ball i2. In-;the cathode cylinder Just below this ball l2 may'.-, be placed a wire 13 to act as the protective grid 0! my invention.

A thin metal window, preferably of thin aluminum metal about 0.0005 to 0.001 inch thick is sealed across the otherwise open end of glass tube l, with the aidioi' a metal ring it sealed around the outside edge or the tube l as shown with the aluminum soldered thereto by the solder lb.

The potential gradient between the anode wire and the grid wire should be just slightly-greater than that between the anode wire and the aluminum window, so that should an overloaded condition develop for any reason and produce arcing, the arc will occur between anode and grid rather than between anode and window. This protects the window, which might otherwise develop a leak on severe or prolonged arcing, the window being so thin.

Such a thin window is necessary for good transmission of beta rays. Because of the thinness of the window, the pressure of the gas filling inside the tube should be in the neighborhood of atmospheric.

A mesh or grid of wires can be used instead of a single wire if desired, as long as the beta ray transmission is not too much reduced thereby. The wire or grid should not be so close to the anode that arcing will occur at the normal operating voltage of the tube.

The word grid in the appended claims is intended to mean a grid or mesh of several Wires, or merely a single wire.

What I claim is:

1. In a beta ray counter tube having an anode, a cathode, a gas filling and a thin metal window, a grid connected to said cathode and extending near said anode in proximity to said window.

2. A beta ray counter tube comprising an envelope open at one end, a thin metal window sealing said end, a cathode extending toward but spaced from said window, an anode extending toward but spaced from said window, and a grid near said anode in the vicinity of said window and electrically connected to said cathode.

3. The combination of claim 2, in which the grid is near enough to the 'anode to make the voltage gradient between it and the anode greater than that between the window and anode.

4. The combination or claim 2 in which the grid is spaced from the anode a distance too great for arcing at the tubes normal operating voltage, but a distance short enough to have a lower arcing voltage to the anode than has the win-- dow.-

. HERBERT ME'I'I'EN.

No references cited. 

